Method of forming a configured fibrous web containing paper-making fibers and fibers of a heat-sealable material



Oct. 31-, 1967 R. JOHNSON 3,350,260

METHOD OF FORMING A CONFIGURED FIBROUS WEB CONTAINING PAPER-MAKINGFIBERS AND FIBERS OF A HEAT-SEALABLE MATERIAL Filed July 28, 1964 2Sheets-Sheet 1 Get. 31, 1967 R. JOHNSON 3,350,260

METHOD OF FORMING A CONFIGURED FIBROUS WEB CONTAINING PAPER-MAKINGFIBERS AND FIBERS OF A HEATSEALABLE7 MATERIAL Filed July 28, 1964 2Sheets-Sheet 2 llnited States I atent O 3,350,260 METHOD OF FORMING ACONFIGURED FI- BROUS WEB CONTAINING PAPER-MAKING FIBERS AND FIBERS OF AHEAT-SEALABLE MATERIAL Reginald Johnson, Bolton, England, assignor toJames R. Crompton and Brothers Limited, Bury, England, a British CompanyFiled July 28, 1964, Ser. No. 385,602 Claims priority, application GreatBritain, July 29, 1963,

3 Claims. (Cl. 162-116) ABSTRACT OF THE DISCLOSURE Method ofmanufacturing a fibrous web which can be used for making tea bags whichconsists in blanking off selected areas of a paper-making forming screenor wire at spaced locations so as to leave areas of unrestricted flow,that is, open mesh areas, and laying the fibres in suspension on saidpaper-making forming wire, which fibres are paper-making fibres andshort fibres of heatsealable material, the paper-making fibres having alength sufficient to form a continuous web on the forming wire while theheat-sealing material fibres are of a length such that they are led downpredominantly along the open mesh areas of the paper-making formingwire, and in one specific embodiment the open mesh areas are of an inchwide and the paper-making fibres are predominantly of a length of of aninch.

This invention relates to a method of manufacturing a fibrous web.

It has previously been proposed to manufacture fibrous webs, e.g. ofpaper, by laying down the web from a fluid suspension which is appliedto a travelling wire or cloth screen. The suspending fluid, which can beliquid or gaseous, drains through the screen leaving behind web-formingfibres which are subsequently removed from the wire as a continuous web.

An object of the present invention is to provide means whereby thefibres forming a web can be deposited according to a given pattern.

According to the present invention, there is provided a method ofmanufacturing a fibrous web comprising applying a suspension of fibresin a fluid onto a supporting screen, said screen being provided withmeans for restricting fluid drain-age through the screen according to agiven pattern whereby a fibrous web is laid down on the screen inaccordance with said pattern.

In the manufacture of paper for use in making tea bags, it haspreviously been the practice to apply a fluid suspension of fibres ontoa travelling wire screen to form an air-permeable paper web. The paperweb thus formed is then coated with a further layer of fibres comprisingwholly or mainly a heat scalable material, the heat sealing fibres beingdistributed substantially uniformly over the paper web. It will beapparent that by using the above process an excess of heat-sealingfibres are used and this has two distinct disadvantages. Firstly, thefact that the heat sealing fibres are distributed uniformly over thewhole of the paper web instead of merely at those locations where heatsealing is required means that an unnecessary amount of heat sealingfibres is being used. Secondly, again due to the uniform distribution ofthe heat sealing fibres over the paper web, the air permeability andfusion rate of those portions of a tea bag which are not to be heatsealed is decreased.

Embodiments of the invention will now be described, by Way of example,with reference to the accompanying drawings in which:

3,350,2 60 Patented Oct. 31, 1.967

FIGURE 1 is a diagrammatic representation of one form of apparatus forcarrying out the present invention,

FIGURE 2 is a fragmentary view to an enlarged scale of a wire screensuitable for producing tea bag paper,

FIGURE 3 is a fragmentary view of a tea bag paper produced in accordancewith-the method of the invention,

FIGURE 4 is a fragmentary view of another form of paper produced by thepresent invention, and

FIGURE 5 is a diagrammatic representation of an alternative form ofapparatus for carrying out the present invention.

In the method according to the present invention and with particularreference to FIGURES l to 3, the heat sealing tea bag paper is madeaccording to accepted practice except that the normal type of travellingwire screen is replaced by one in the form of an open mesh wire web 6 ofwhich discontinuous areas 7 (FIGURE 2) are blanked off by means ofcoating them with hardened gelatin. The screen 6 is driven through driverolls 8, 9 and travels over guide rolls 10, 11, 12 and 13. The blanked'ofl areas 7 are of square form and 7 to the inch and are separated fromeach other by peripheral open mesh areas 14, that are wide.

When the suspension of base paper fibres 15, held in a reservoir 16, isfed onto the screen 6 the suspension fluid drains into a receptacle 17through the wire screen 6 as at 18 only at the open mesh areas 14 andthe fibres as shown in FIGURE 3 tend to be concentrated in the patternof these areas but because of the relative length of these fibres 15,average about a thin web nevertheless does extend over the whole screensurface. When the suspension 19 of heat-sealing fibres 20 (FIGURE 3) andattendant beaten paper-making fibres is added to the partially formedsheet from a head-box 21, according to accepted practice, then thesemuch shorter fibres tend to be deposited almost exclusively over theopen drainage areas 14 when the remainder of the suspension fluid drainsthrough. The fibrous Web thus formed is then drawn off the Wire screen 6and is then as shown in FIGURE 3 in the form of regular square areassubstantially free of heat-sealing fibres 20 (shown in blacker lines inFIGURE 3), each area being surrounded by a peripheral area in which theheat sealing fibres 20 have been concentrated.

Using a wire screen of this particular design, the open areas 14comprise of the total area of the screen and consequently the heatsealing fibres 20 and attendant short paper-making fibres will coverapproximately /2 of the total area of the paper. The size and shape ofblanked-off areas and peripheral clear areas can of course be varied asdesired.

The fact that approximately half of the area of the tea bag made withthis paper is substantially free of heat-sealing fibres 20 and attendantshort paper-making fibres ensures a greater air permeability in theuncovered areas and results in the use of less heat-sealing fibres thanhas previously been required. Both factors result in a tea bag when madeaccording to the invention, having an improved infusion rate.

Although in the above described embodiment, the screen 6 is stated to beof wire and the blanked-off areas 7 are formed by coating the screenwith gelatin, the screen 6 can be of any suitable material e.g.synethetic plastic and the blanked-off areas 7 can be obtained withmaterials other than gelatin e.g. thermoplastic or thermosettingsynthetic plastic material or solder. Alternatively, the areas can beblanked-off by electrolytic deposition.

The present invention has been described above with specific referenceto the manufacture of tea bags. It will be appreciated, however, thatthe method has much wider applications. For example, in a secondembodiment of the invention described with particular reference toFIGURE 4 and in which heat sealing fibres are not employed, the screenis given any desired pattern by means of blanking-off discontinuousareas. Fibres 22 of a sufiiciently short average length chosen to suitthe pattern size and the extent of the gaps between blankedoff areas isthen laid down in suspension on the screen. The fibres 22 are orientedalong the gaps and when the web is drawn off the screen, a fibrousnetwork as shown in FIGURE 4 of the desired pattern results. The designof the pattern governs the properties of the network produced as regardsstrength, stretch, drape and permeability.

If in the preceding embodiment, longer fibres are employed for the samegiven pattern of screen, the resultant fibrous web is in the nature ofan inter-connected network of ridges of relatively high substance i.e.wt/unit area, each mesh of the network being closed by a fibrousmembrane of a thinner relatively low substance. By this means a fibrousweb is obtained in which for a given overall substance, theair-permeability is greatly increased whilst the strength relative to auniform sheet of the same substance is approximately the same.

In a third embodiment of the present invention as described withreference to FIGURE 5, the pattern is not embodied in or superimposed onthe screen. In this arrangement a uniform plain screen 23 is employedand there is brought into contact with the uniform screen 23 a secondendless screen 24 having a patterned surface and being adapted to movein known fashion around a system of rollers 25. Drainage can take placethrough the screen 24 in accordance with the pattern. A fiuid suspension26 of base paper fibres is fed on to the uniform screen 23, the excessfluid draining through into a trough 27 located below the screen, thewater being capable of being drawn off from the trough through an outletvalve 28. At a point subsequent to the laying On of the base paperfibres in relation to the path of travel of the screen 23, a secondsuspension of paper fibers is positioned in a head-box 29 above wherethe screens 23 and 24 approach one another closely. When the secondsuspension is fed as a second layer on the existing uniform layercarried by the screen 23, the second layer is patterned due to thepatterned screen 24. In the same manner as in the preceding embodiments,the tendency is for the fibres of the second layer to be oriented mainlyalong the open areas of the pattern thus producing a correspondinglypatterned fibrous web which can be drawn off the uniform screen 23. Thepatterned surface although shown in FIGURE as a continuous wire screen24 can be in any other suitable form e.g. it can be a rubber orsynthetic plastic belt, wire-covered roll, or a hollow or solid rollwith an etched, cut or moulded pattern thereon, means always beingprovided for the removal of the fiuid drainage from the open areas ofthe pattern. In this embodiment, the blocked out patterns can becontinuous i.e. connected areas and the open areas separate. Thisarrangement permits the production of a fibrous web made up of aplurality of layers which can be efiected by using multiple head-boxesand a combination of unrestricted or patterned drainage stages. Each ofthe several layers can be of the same composition or alternatively,individual layers can have special characteristics as desired, e.g.colour or heat sealing properties. Additional layers superimposed on theinitial fibrous layer need not be fibrous e.g. they can be mineralpigments.

In the three embodiments of the invention described above the pattern onthe screen is formed by taking a uniform screen and blanking ofl areasas desired. The screen can also be provided with a pattern in suitablecases, by weaving the wire or cloth to form a woven pattern so thatareas of varying drainage rates are produced. In this way, a similaretIect can be obtained even although certain areas are not completelyblanked-ot Any desired patterns can be reproduced in the screens of theabove-described embodiments, although where only a single patternedscreen is employed, the open areas must be continuous.

What I claim is:

1. In the method of manufacturing a fibrous web comprising applying asuspension of paper-making fibres and fibres 'of a heat scalablematerial of a shorter length than the length of said paper-making fibreson to a supporting screen, restricting fluid drainage through the screenat spaced locations by blanking off selected areas of said screen, andlaying down a web on the screen from the suspension so that thepaper-making fibres form a continuous paper web while the heat sealingfibres being shorter in length than the paper-making fibres are locatedpredominantly along the continuous unrestricted areas of the screen.

2. A method as claimed in claim 1, comprising applying the paper-makingfibres and the heat scalable fibres to the screen independently of eachother.

3. A method as claimed in claim 1, comprising employing paper-makingfibres having an average length of about inch and when blanking off theselected areas of the screen leaving unrestricted fiow areas of lesstransverse dimensions than the length of said paper-making fibres.

References Cited UNlTED STATES PATENTS 3,185,615 5/1965 Reifers 162-411X 3,190,790 6/1965 Ploetz et al. 162-299 X FOREIGN PATENTS 437,9453/1912 France. 959,213 9/1949 France.

24,085 1892 Great Britain.

S. LEON BASHORE, Primary Examiner.

1. IN THE METHOD OF MANUFACTURING A FIBROUS WEB COMPRISING APPLYING ASUSPENSION OF PAPER-MAKING FIBRES AND FIBRES OF A HEAT SEALABLE MATERIALOF A SHORTER LENGTH THAN THE LENGTH OF SAID PAPER-MAKING FIBRES ON TO ASUPPORTING SCREEN, RESTRICTING FLUID DRAINAGE THROUGH THE SCREEN SPACEDLOCATIONS BY BLANKING OFF SELECTED AREAS OF SAID SCREEN, AND LAYING DOWNA WEB ON THE SCREEN FROM THE SUSPENSION SO THAT THE PAPER-MAKING FIBRESFORM A CONTINUOUS PAPER WEB WHILE THE HEAT SEALING FIBRES BEING SHORTERIN LENGTH THAN THE PAPER-MAKING FIBRES ARE LOCATED PREDOMINANTLY ALONGTHE CONTINUOUS UNRESTRICTED AREAS OF THE SCREEN.